Intravenous injection of indocyanine green to enhance laser-assisted coagulation of blood vessels in skin - an animal study.

BACKGROUND: Laser therapy of vascular lesions, such as port wine stains (PWS) or leg veins are still imperfect due to different diameters and depth of vessels in tissue. We propose to improve blood vessel coagulation by intravenous introduction of an exogenous chromophore (indocyanine green, ICG) that effectively converts near-infrared (NIR) laser light into heat. OBJECTIVE: The purpose of this study was to determine the plasma clearance rate, systemic toxicity and histological effects of ICG-assisted laser therapy in an animal model. METHODS: Piglets received intravenous injection of ICG. Blood samples were collected at different times. Systemic toxicity was assessed by measuring liver enzyme levels and other indicators of liver function. The plasma clearance rate of ICG was determined by light absorption measurement in blood samples. The skin was irradiated with a diode laser (810 nm) using radiant exposures from 31 to 80 J/cm². Skin reaction at the treatment site was graded, and punch biopsies were taken for histological examination at 24 and 72 h after treatment. RESULTS: No hepatic toxicity was observed. The clinical examination revealed no adverse skin reactions at 24 or 72 h after laser irradiation. This was confirmed by histological evaluation that showed efficient vessel coagulation without damage of the epidermis or dermis. CONCLUSIONS: In light of these in vivo results, we suggest that ICG-assisted laser therapy could substantially improve clinical outcomes of PWS or leg veins treatment with minimal risk of adverse reactions.

Altered calcium dynamics mediates P19-derived neuron-like cell responses to millimeter-wave radiation.

Intracellular calcium oscillations have long been recognized as a principal mediator of many vital cellular activities. Furthermore, Ca(2+) dynamics can be modulated by external physical cues, including electromagnetic fields. While cellular responses to low-frequency electric fields have been established, the possible non-thermal effects of millimeter-wave (MMW) radiation are still a subject of discussion and debate. We used mouse embryonic stem cell-derived neuronal cells and a custom-built 94 GHz applicator to examine in real time the altered Ca(2+) oscillations associated with MMW stimulation. MMW irradiation at 18.6 kW/m(2) nominal power density significantly increased the Ca(2+) spiking frequency in the cells exhibiting Ca(2+) activity. The N-type calcium channels, phospholipase C enzyme, and actin cytoskeleton appear to be involved in mediating increased Ca(2+) spiking. Reorganization of the actin microfilaments by a 94 GHz field seems to play a crucial role in modulating not only Ca(2+) activity but also cell biomechanics. Many but not all observed cellular responses to MMW were similar to thermally induced effects. For example, cell exposure to a 94 GHz field induced nitric oxide production in some morphologically distinct neuronal cells that could not be reproduced by thermal heating of the cells up to 42 degrees C. The highest observed average temperature rise in the MMW exposure chamber was approximately 8 degrees C above the room temperature, with possible complex non-uniform microscopic distribution of heating rates at the cell level. Our findings may be useful to establish quantitative molecular benchmarks for elucidation of nociception mechanisms and evaluation of potential adverse bioeffects associated with MMW exposure. Moreover, control of Ca(2+) dynamics by MMW stimulation may offer new tools for regulation of Ca(2+)-dependent cellular and molecular activities, for example, in tissue engineering applications.

In vivo relevance for platelet glycoprotein Ibalpha residue Tyr276 in thrombus formation.

BACKGROUND: Platelet glycoprotein (GP) Ib-IX-V supports platelet adhesion on damaged vascular walls by binding to von Willebrand factor (VWF). For several decades it has been recognized that the alpha-subunit of GP (GPIbalpha) also binds thrombin but the physiological relevance, if any, of this interaction was unknown. Previous studies have shown that a sulfated tyrosine 276 (Tyr276) is essential for thrombin binding to GPIbalpha. OBJECTIVES: This study investigated the in vivo relevance of GPIbalpha residue Tyr276 in hemostasis and thrombosis. METHODS: Transgenic mouse colonies expressing the normal human GPIbalpha subunit or a mutant human GPIbalpha containing a Phe substitution for Tyr276 (hTg(Y276F)) were generated. Both colonies were bred to mice devoid of murine GPIbalpha. RESULTS: Surface-expressed GPIbalpha levels and platelet counts were similar in both colonies. hTg(Y276F) platelets were significantly impaired in binding alpha-thrombin but displayed normal binding to type I fibrillar collagen and human VWF in the presence of ristocetin. In vivo thrombus formation as a result of chemical damage (FeCl(3)) demonstrated that hTg(Y276F) mice have a delayed time to occlusion followed by unstable blood flow indicative of embolization. In models of laser-induced injury, thrombi developing in hTg(Y276F) animals were also less stable. CONCLUSIONS: The results demonstrate that GPIbalpha residue Tyr276 is physiologically important, supporting stable thrombus formation in vivo.

Optimal parameters for the treatment of leg veins using Nd:YAG lasers at 1064 nm.

BACKGROUND: The treatment of large vessels such as leg veins is successfully performed in clinical practice using pulsed Nd:YAG lasers. However, it is still unclear how laser parameters such as wavelength, fluence and pulse duration influence vessel destruction in leg veins. OBJECTIVES: To elucidate the governing parameters in selective photothermolysis of large vessels. METHODS: A recently developed mathematical model for photothermolysis has been adapted for the treatment of leg veins. The model was used to analyse the effectiveness of the selective photothermolysis process in laser treatment of leg veins by Nd:YAG at 1064 nm. The efficiency of laser-induced vessel heating was defined as a ratio between the absorbed and delivered energy. RESULTS: The efficiency improved with increasing vessel diameter, in agreement with clinical findings in various studies. The pulse duration made a minor contribution for laser fluences of 100-400 J cm(-2), whereas the efficiency was better for a small spot. The use of moderate fluences of 100-200 J cm(-2) reduced excess dermis heating and pain. CONCLUSIONS: We provide reference parameters for optimal treatment of leg veins using Nd:YAG lasers at 1064 nm. Our model predicts a maximal efficiency of a range of fluences (100-200 J cm(-2)) and pulse durations (10-100 ms).